A former Gloucester Academy graduate, the 27-year-old joined the province ahead of the 2009/10 season from Exeter Chiefs and has amassed 74 caps in just over three seasons.
With his excellent ability in the lineout, strong ball carrying and ferocious defence, he wasted little time in establishing himself as a regular starter at Ulster.
With Ireland Under-21 honours to his name before his arrival in Belfast, his form for Ulster resulted in further international recognition when he won two senior caps in June 2010, scoring a try against New Zealand on his debut.
He now has five caps for Ireland, with his first start also coming against New Zealand in the summer tour in June this year.
That came at the end of an excellent 2011/12 campaign for Tuohy in which he lined out 28 times for the province.
He also played an integral role as the team reached the Heineken Cup final for the first time since 1999, his performance in the quarter-final win over Munster at Thomond Park highlighting his quality on the European stage.
Commenting on his Ulster career to date and his ambitions for the next three seasons, Tuohy said: "I came over here four years ago and settled immediately. I feel very comfortable here and it's like a home from home for me.
"Ulster have looked after me really well and I'm delighted to be staying on. There's been a dramatic transformation in the short time that I've been here and it's fantastic to be part of.
"We did well last year in the Heineken Cup and are hoping to go one better this season. We also realise how important the PRO12 is and we are determined to be successful in it too.
"It's something I really want to be part of and I never really thought about leaving. There would have been a lot of unfinished business if I had left so that never even entered my mind.
"I'm thoroughly looking forward to helping Ulster be successful over the next few years."